Plants are constantly exposed to a variety of biotic (i.e., pathogen infection and insect herbivory) and abiotic (e.g., high pH, low phosphate) stresses. To survive these challenges, plants have developed elaborate mechanisms to perceive external signals and environmental stresses and to manifest adaptive responses with proper physiological and morphological changes (Bohnert et al., 1995). Plants exposed to low or high pH conditions typically have low yields of plant material, seeds, fruit and other edible products. Extreme soil pH conditions have a major influence on nutrient availability resulting in severe agronomic losses. Plants exposed to low pH soil conditions develop deficiencies in nutrients such as copper, molybdate, potassium, sulfur, and nitrogen. Also, plants exposed to high pH soil conditions develop iron, copper, manganese, and zinc deficiencies (FIG. 1). Phosphate deficiency is a problem in both high and low pH soil conditions. Essential mineral nutrients are required in substantial amounts to sustain plant growth and maximize plant yields.
Consequently, agricultural and horticultural entities routinely alter the rhizosphere to maximize and maintain crop yields; these frequently result in more pollution and unbalancing of the natural soil mineral balance (National Research Council. (1989) Alternative Agriculture. National Academic Press, Washington D.C.). Excessive over-liming of acid soils, for instance, has resulted in the induction of iron, manganese, copper, and zinc deficiencies; deficiencies commonly observed in calcareous soil.
It would, therefore, be of great interest and importance to be able to identify genes that confer improved phosphate efficiency characteristics to thereby enable one to create transformed plants (such as crop plants) with improved phosphate efficiency characteristics to thereby better survive low and high pH conditions.
In the field of agriculture and forestry efforts are constantly being made to produce plants with an increased growth potential in order to feed the ever-increasing world population and to guarantee the supply of reproducible raw materials. This is done conventionally through plant breeding. The breeding process is, however, both time-consuming and labor-intensive. Furthermore, appropriate breeding programs must be performed for each relevant plant species.
Progress has been made in part by the genetic manipulation of plants; that is by introducing and expressing recombinant nucleic acid molecules in plants. Such approaches have the advantage of not usually being limited to one plant species, but instead being transferable among plant species. (Zhang et al. (2004) Plant Physiol. 135:615). There is a need for generally applicable processes that improve forest or agricultural plant growth potential. Therefore, the present invention relates to a process for increasing the abiotic stress tolerance and consequently the growth potential in plants, characterized by expression of recombinant DNA molecules stably integrated into the plant genome.